IL-1R and MyD88 Contribute to the Absence of a Bacterial Microbiome on the Healthy Murine Cornea.
IL-1R and MyD88 Contribute to the Absence of a Bacterial Microbiome on the Healthy Murine Cornea.
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DOI：
10.3389/fmicb.2018.01117
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发表时间：
2018
影响因子：
5.2
通讯作者：
Fleiszig SMJ
中科院分区：
文献类型：
--
作者：
Wan SJ;Sullivan AB;Shieh P;Metruccio MME;Evans DJ;Bertozzi CR;Fleiszig SMJ
微生物群落对粘膜组织的健康很重要。传统的培养和基因测序已经证明了结膜上的细菌种群。然而，目前尚不清楚对视力至关重要的透明组织角膜是否也有微生物群。用炔功能化D-丙氨酸(AlkDala)标记野生型、IL-1R(-/-)和MyD88(-/-)C57BL/6小鼠的角膜，这种探针只结合到代谢活性细菌的肽聚糖中。荧光原位杂交(FISH)也用于检测活细菌。AlkDala标记很少在健康的角膜上观察到。相反，相邻的结膜含有丝状的alkDala阳性形式，也被棒状杆菌特异性探针DMN-tre标记。FISH证实健康的角膜上没有活细菌，这也在24小时内清除了故意接种的细菌。与野生型不同，IL-1R(-/-)和MyD88(-/-)角膜都含有大量alkDala标记的细菌，这一结果被外用抗生素消除了。IL-1R(-/-)角膜对荧光素不透皮，提示细菌定植并不能反映上皮完整性降低。因此，与结膜和其他粘膜表面相比，健康的小鼠角膜上几乎没有存活的细菌，这种构成状态需要IL-1R和MyD88。虽然这项研究不能排除真菌、病毒、非活细菌或休眠细菌的存在，但数据表明，健康的小鼠角膜不存在常驻的活细菌群落或微生物群，这些微生物群的缺乏可能对了解这种组织的动态平衡具有重要意义。
Microbial communities are important for the health of mucosal tissues. Traditional culture and gene sequencing have demonstrated bacterial populations on the conjunctiva. However, it remains unclear if the cornea, a transparent tissue critical for vision, also hosts a microbiome. Corneas of wild-type, IL-1R (-/-) and MyD88 (-/-) C57BL/6 mice were imaged after labeling with alkyne-functionalized D-alanine (alkDala), a probe that only incorporates into the peptidoglycan of metabolically active bacteria. Fluorescence in situ hybridization (FISH) was also used to detect viable bacteria. AlkDala labeling was rarely observed on healthy corneas. In contrast, adjacent conjunctivae harbored filamentous alkDala-positive forms, that also labeled with DMN-Tre, a Corynebacterineae-specific probe. FISH confirmed the absence of viable bacteria on healthy corneas, which also cleared deliberately inoculated bacteria within 24 h. Differing from wild-type, both IL-1R (-/-) and MyD88 (-/-) corneas harbored numerous alkDala-labeled bacteria, a result abrogated by topical antibiotics. IL-1R (-/-) corneas were impermeable to fluorescein suggesting that bacterial colonization did not reflect decreased epithelial integrity. Thus, in contrast to the conjunctiva and other mucosal surfaces, healthy murine corneas host very few viable bacteria, and this constitutive state requires the IL-1R and MyD88. While this study cannot exclude the presence of fungi, viruses, or non-viable or dormant bacteria, the data suggest that healthy murine corneas do not host a resident viable bacterial community, or microbiome, the absence of which could have important implications for understanding the homeostasis of this tissue.